1. Field of the Invention
The present invention relates to an optical path switching apparatus comprising a plurality of input and output fiber collimators in which the optical paths of the light beams from the input fiber collimators are selectively switched to the optical paths of the light beams of the output fiber collimators.
2. Description of Related Art
Up until now, there have been proposed a wide variety of optical path switching apparatus one typical example of which is shown in FIGS. 10 and 11 to bear a reference numeral 900. The optical path switching apparatus 900 comprises an input fiber collimator array 910 including a plurality of input fiber collimators 910a, 910b, 910c and 910d disposed in spaced and parallel relationship with one another to have a plurality of light beams 901, 902, 903 and 904 pass therethrough. The input fiber collimator 910a has an optical fiber 911a and a lens 912a connected to the front end of the optical fiber 911a to form in combination an input port 913a. The input fiber collimators 910b, 910c and 910d are the same in construction as the input fiber collimator 910a previously mentioned. The input fiber collimators 910a, 910b, 910c and 910d respectively serve to introduce the light beams 901, 902, 903 and 904 from the external of the optical path switching apparatus to the internal of the optical path switching apparatus. The optical path switching apparatus further comprises a retaining member 914 designed to retain the input fiber collimators 910a, 910b, 910c and 910d in such a manner that the light beam axes of the optical paths formed by the input fiber collimators 910a, 910b, 910c and 910d are held in spaced and parallel relationship with one another.
On the other hand, the conventional optical path switching apparatus further comprises an output fiber collimator array 920 similar in construction to the input fiber collimator array 910 and thus including a plurality of output fiber collimators 920a, 920b, 920c and 920d disposed in spaced and parallel relationship with one another to have a plurality of light beams 901, 902, 903 and 904 pass therethrough. The output fiber collimator 920a has an optical fiber 921a and a lens 922a connected to the rear end of the optical fiber 921a to form in combination an output port 923a. The output fiber collimators 920b, 920c and 920d are the same in construction as the output fiber collimator 920a. The output fiber collimators 920a, 920b, 920c and 920d respectively serve to discharge the light beams 901, 902, 903 and 904 from the internal of the optical path switching apparatus to the external of the optical path switching apparatus. The optical path switching apparatus further comprises a retaining member 924 designed to retain the output fiber collimators 920a, 920b, 920c and 920d in such a manner that the light beam axes of the optical paths formed by the output fiber collimators 920a, 920b, 920c and 920d are held in spaced and parallel relationship with one another and in perpendicular relationship with the input fiber collimators 910a, 910b, 910c and 910d. The optical path switching apparatus exemplified in FIG. 10 has four input ports 913a and four output ports 923a combined to form light beam paths numbering 4 by 4.
The optical path switching apparatus further comprises an light beam switching array 930 including a plurality of light beam switching elements 931 numbering sixteen shown for example in FIG. 10 and adapted to reflect the light beams from the optical paths of the input fiber collimators 910a, 910b, 910c and 910d to the optical paths of the output fiber collimators 920a, 920b, 920c and 920d. The light beam switching elements 931 are disposed at the respective junctions of the optical paths of the input fiber collimators 910a, 910b, 910c and 910d and the optical paths of the output fiber collimators 920a, 920b, 920c and 920d to be driven to rotate around their own axes to selectively switch the optical paths of the input fiber collimators 910a, 910b, 910c and 910d to the optical paths of the output fiber collimators 920a, 920b, 920c and 920d. 
The optical path switching apparatus further comprises an actuator array 940 including a plurality of drive actuators 941 numbering sixteen shown for example in FIG. 10 and having a rotation shaft 942 for driving to rotate the light beam switching elements 931. In FIG. 11, however, is shown only four drive actuators 941.
The construction of the light beam switching elements 931 will be described hereinafter in more detail.
The light beam switching element 931 shown in FIG. 11 is disposed at the junction of the optical path of the input fiber collimator 910a and the optical path of the output fiber collimator 920b and has a support plate 932 fixedly connected with the rotation shaft 942 of the drive actuator 941 so that the light beam switching element 931 can be driven to rotate around its own center axis. The light beam switching element 931 is shown in FIGS. 12 and 13 as comprising a reflection mirror 933 securely mounted on the peripheral surface of the support plate 932 and having a reflection mirror surface 933a designed to reflect the light beam 901 from the optical path of the input fiber collimator 910a, and a reflection mirror 934 also securely mounted on the peripheral surface of the support plate 932 and having a reflection mirror surface 934a also designed to reflect the light beam 901 reflected by the reflection mirror surface 933a to the optical path of the output fiber collimator 920b along the light beam switching element 936 at an angle 901a of 90 degrees under the influence of an angle 935 of 45 degrees between the reflection mirrors 933 and 934.
As will be seen from the foregoing description, the drive actuators 941 of the drive actuator array 940 are operative to assume two different states consisting of respective reflection states and respective non-reflection states. In the reflection states, the drive actuators 941 are operated to have the support plate 932 rotated and thereby to have the reflection mirrors 933 and 934 positioned to enable the light beams to be reflected by the reflection mirror surfaces 933a and the reflection mirror surface 934a to selectively switch the optical paths of the input fiber collimators 910a, 910b, 910c and 910d to the optical paths of the output fiber collimators 920a, 920b, 920c. In the non-reflection states, on the other hand, the drive actuators 941 are not operated to have the rotation shafts 932 rotated and thereby not to have the reflection mirrors 933 and 934 positioned not to enable the light beams to be reflected by the reflection mirror surfaces 933a and the reflection mirror surface 934a. This means that the optical paths of the input fiber collimators 910a, 910b, 910c and 910d cannot be selectively switch to the optical paths of the output fiber collimators 920a, 920b, 920c. 
The respective mirror surfaces 933a and 934a of the reflection mirrors 933 and 934 on the peripheral surface of the support plate 932 are angled at about 45 degrees so that the optical path of the input fiber collimator 910a can be changed in direction at an angle 935 of about 90 degrees with respect to the optical path of the output fiber collimator 920b. The foregoing description has been made only regarding the light beam switching element 931 with reference to FIGS. 12 and 13, however, the remaining light beam switching elements constituting the light beam switching array 930 are completely the same in construction as the light beam switching element 931.
The conventional optical path switching apparatus encounters such a problem that the support plates are required to be arranged with a sufficient space between the neighboring support plates to prevent the reflection mirrors from being held in contact with one another. The sufficient space of the neighboring support plates thus required makes it inevitable for an optical path switching apparatus to become relatively large in a size.